My grandmother was a schoolteacher in Winona, Miss., back when black folks knew that trying to vote would cost them their jobs. She was so fearful of retribution that she didn’t want Aunt Pearlie’s boyfriend, a young civil rights activist, hanging around on the front porch. She was afraid that people would recognize him.

After the passage of the Voting Rights Act in 1965, a few of her colleagues registered. But it was not until Martin Luther King’s last campaign — a procession of mules plodding from Marks, Miss., to Atlanta — that she fully embraced the vote. The mules arrived at Winona’s courthouse, wearing signs that read, “I have been to the mountaintop.” Grandma Jones invited some of the young activists to sleep at her house for the night. A few months later, she cast the first ballot of her life, at age 46.

“Older people weren’t the first to stick their necks out,” Aunt Pearlie told me. “Young people were the ones who led. They were bursting at the seams to change things.”

Thousands of college — and even high school — students risked arrest, beatings, and even death to get the right to vote for blacks in Mississippi. Most of the activists who were sent to jail for a voter registration drive in Greenwood were too young to vote themselves. One of them, Jesse James Glover, was a seasoned veteran of civil disobedience at age 17. He had joined the Student Nonviolent Coordinating Committee three years earlier.

“It really was a new generation,” said Alexander Keyssar, a Harvard professor who studies the history of enfranchisement in America. “King was 33 — and he seemed like the grown-up.”

Both the anti-war movement in the North and the civil rights movement in the South were fueled by the idealism and energy of youth. Drafted in droves to fight in Vietnam, teenagers projected a kind of moral authority.

“Old enough to fight, old enough to vote,” they chanted in support of a Constitution amendment to drop the voting age from 21 to 18. They got their way in 1971.

Compare that to the youth of today, who seem to get more exercised about voter fraud on “American Idol” than voter suppression in the current presidential race.

Singer Taylor Swift told her fans that, at 22, she is too young to know much about picking the next president: “I don’t talk about politics because it might influence other people.”

Justin Bieber, who just turned 18, looked like a deer in headlights this summer when Dave Letterman asked him who he would vote for if he were a US citizen. (He’s Canadian.) “Why are you guys talking to me about voting and all that stuff?” he joked.

Lil Wayne, who is not so little anymore at age 30, can’t vote because of a gun charge. But he didn’t have any words of wisdom about the election either: “Following it? Yes, I am . . . Leaning one way? No, I’m not.”

With role models like that, it’s no wonder that only 16 percent of 18- to- 20-year-olds voted in the 2010 midterm election, according to the Census Bureau, compared with 51 percent of people between 45 and 64.

Don’t they get it? Don’t they get that they are the ones who will bear the brunt of whatever compromises we make — or fail to make — in Washington over the next four years, from climate change to Social Security reform to the national debt?

Maybe it’s just the American way to fight like hell for the right to vote, until we have it, at which point we immediately commence taking it for granted.

My nephew, who just turned 18, voted for the first time in this election, four decades after Grandma Jones made her first foray to the ballot box. Of course, he had a little assistance: My sister and her husband drove across several Midwestern states to deliver the absentee ballot to him at college. They waited as he filled it out, and mailed it in themselves. “What’s the big deal?” he was probably thinking as they did it. I suppose the young civil rights activists of the ’60s — who faced beatings and jail time in order to vote — would have found something beautiful about that.